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Old Mar 16th 2017, 07:43 PM   #1
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Physics IA help

Yo guys,

So I'm in IB physics, and to be completely honest I'm not really a science guy so I had some trouble coming up with an idea for my physics IA. I ended up doing something with radio waves because I had access to somebody who operated an amateur radio...I figured I would put together an antenna, connect it to light bulb, and try to see the effect of using different frequencies to try to power it.

Needless to say I quickly realized that I would need a massive transmitter to get it to light up so I connected an oscilloscope to the whole shebang to try to salvage some data from the experiment.

My results were that 420 and 450 Mhz waves generated the most voltage (~1mV), 440 Mhz generated the 2nd greatest (~0.6mV), and 460 and 480 Mhz generated voltages of 0.2 and 0.1 mV respectively. All of this was when the transmitter was held around 10cm from the antenna.

This data is all over the place and I don't know exactly what conclusions I could possibly draw from it. I know that I probably should have done my research before jumping in with the idea that differences in frequency will somehow affect the resulting voltage in an antenna at all, but this is all I have at this point so I would really appreciate if somebody could give me some pointers on what I could do with this data..

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Old Mar 17th 2017, 05:14 AM   #2
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Your idea that antenna action depends upon frequency is sound and a good one.

But all antenna, in fact almost all wave sources and receivers, have a frequency range over which they operate best.

This is called the bandwidth, which you should look up.

Your problem is that your test frequencies were probably too close together to show much effect.

Can you try again with a range of say 250 to 600 Mhz?

If you do this you may be able to plot a 'bandwidth curve' (again look it up)

That would give you a nice outcome to write up.

By the way did you really have access to an oscilloscope capable of operating at 450 mHz ?
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Old Mar 17th 2017, 07:20 AM   #3
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I agree with studiot, but would add two additional points to consider:

1. Are you sure that the transmitter you're using provides constant power output regardless of frequency?

2. I don't want to influence your results, but with a proper experimental set up antenna you should find that the power received is essentially independent of frequency (don't confuse radio wave power with photon energy $\displaystyle E= h \nu$)
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Old Mar 17th 2017, 04:15 PM   #4
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Look up Resonance,
It works for radio waves in much the same way as it does for sound waves.
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